THE EYE. 335 



time soaked for twenty-four hours (well protected from the 

 light) in a 2 per cent, solution of formic acid. After another 

 washing in distilled water the cornea should be cut in two and 

 placed in glycerine ; one portion can then be separated into 

 thin layers, by tearing with fine forceps or needles. 



Examine in glycerine for the corneal corpuscles, nerves, 

 and lymph-spaces, which latter appear dark on a light blue 

 or red background ; or the piece may be imbedded in wax or 

 some such material, and sections made parallel to the surface 

 of the cornea. The remaining half of the specimen is to be 

 imbedded or held in liver or pith. Transverse sections may 

 then be made. These will exhibit on lucky sections the fine 

 plexuses of nerve-filaments under the epithelium, with occa- 

 sional fibres passing up between the individual corpuscles. 

 The different layers of the cornea will be well shown, also the 

 narrow corneal cells (as seen on side view), together with the 

 remains of the endothelial layer on the inner surface. 



The peripheral portions of the cornea are particularly inter- 

 esting. We have here the transitions from cornea to conjunc- 

 tiva and sclera, the origin of the ciliary muscle, the ligament 

 of the iris, and the numerous vessels of the part. 



The epithelium of the cornea (a) forms a gradual transition 

 into the epithelium of the conjunctiva, but the anterior limit- 

 ing membrane (Bowman's) becomes thinner as it approaches 

 the edge of the cornea, until finally it merges with the fibres 

 of the anterior corneal layers into the tunica propria of the 

 conjunctiva. 



No sharp boundary line has been demonstrated between 

 the cornea and the sclera. Under the microscope the fibres 

 appear to have no distinct limit ; the lymph-spaces also of the 

 cornea are continued directly into the sclera, and the scleral 

 and corneal fixed corpuscles are much the same. 



The posterior limiting membrane (DescemeV s) (c), like the 

 anterior, becomes gradually thinner and loses itself in a small 

 bundle of scleral fibres which surround the edge of the mem- 

 brane and form the anterior support to the ligamentum pec- 

 tinatum iridis. 



The endothelium (Fig. 153 <?,) passes uninterruptedly over 

 this ligament (e f ) and is reflected forward over the anterior sur- 

 face of the iris (e") to the edge of the pupil. 



In the angle between the iris and cornea, forming buttresses, 



